<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .standard {
            width: 100px;
            height: 100px;
            padding: 10px;
            margin: 10px;
            background-color: green;
            border: 5px solid #f66;
        }

        .freak {
            width: 100px;
            height: 100px;
            padding: 10px;
            margin: 10px;
            box-sizing: border-box;
            /*怪异盒模型*/
            background-color: yellow;
            border: 5px solid #f66;
        }
        .one {
            width: 100%;
            margin: 100px;
            background-color: orangered;
            height: 100px;
        }
    </style>
</head>

<body>

    <div class="standard"></div>
    <div class="freak"></div>
    <div class="one"></div>

</body>

</html>